为什么圆的周长算出来的小数点的位数不对

package com.yong;

public abstract class Shape {
	public abstract void Perimeter();
	public abstract void Area();
	

}

package com.yong;

public class Rectangle extends Shape {

double a=10;

double b=20;

@Override

public void Perimeter() {

double c=(a+b)*2;

System.out.println("长方形的周长为："+c);

}

@Override

public void Area() {

double s=a*b;

System.out.println("长方形的面积为："+s);

}

}

package com.yong;

public class Circle extends Shape {

final double PI=3.14;

double r=10.0;

@Override

public void Perimeter() {

double c=2*PI*r;

System.out.println("圆的周长为："+c);

}

@Override

public void Area() {

double s=PI*r*r;

System.out.println("圆的面积为："+s);

}

}

package com.yong;

public class Test {

public static void main(String[] args) {

Shape sh1=new Rectangle();

sh1.Area();

sh1.Perimeter();

Shape sh2=new Circle();

sh2.Perimeter();

sh2.Area();

}

}

长方形的面积为：200.0

长方形的周长为：60.0

圆的周长为：62.800000000000004

圆的面积为：314.0